Non-synchronous expansion of the pulmonary parenchyma is thought to occur during ventilation at high breathing frequencies. The magnitude and phase of these asynchronous pulmonary expansions have never been directly quantitated. In this proposed research project we well quantitate the magnitude and phase of asynchronous pulmonaryexpansion in excised dog lungs, oscillated with relatively small tidal volumes (50-150 ml) over a wide range of breathing frequencies (from 0.25 to 30Hz). We will use the technique of stroboscopic photography of surface markers to quantitate these asynchronies. We propose to examine to oscillatory frequency, tidal volume, lung volume, and gas physical property dependence of these asynchronies to determine under what condtions which of two theories best predicts the observed results. The two theories are : 1) asynchronies due to R-L-C inhomogeneities among various airway/parenchymal pathways and 2) propagation of various elastic waves within the parenchyma. The first of these theories was originally proposed by Otis, et al (1956) and has been modified and extended by many others. We propose to build upon available theoretical models, incorporating non-linear effects and relastic boundary conditions to provide predictions of asynchronous flows. The second theory, elastic waves in the parenchyma, is relatively new, is developed in simple form in this application and will be improved upon during the tenure of this proposal. We also propose to measure directly various physical constants of the pulonary parenchyma needed in order to rigorously apply this new theory.